DOUBLE-SIDED OPTICAL FILM WITH LENSLETS AND CLUSTERS OF PRISMS
An optical film has a structured surface with elongated lenslets formed therein and an opposed structured surface with elongated prisms formed therein. The lenslets extend parallel to each other and to an elongation axis which is generally parallel to the film plane, and the prisms also extend parallel to each other and to the elongation axis. The prisms are grouped into separated clusters of adjacent prisms. Each prism cluster is associated with a corresponding one of the lenslets, and has at least 3 prisms. Each lenslet defines a focal point and a focal surface. Vertices of the prisms in a prism cluster are disposed at or near the focal surface of the associated lenslet. When illuminated with oblique light, each lenslet/prism cluster pair, and optionally the optical film as a whole, may produce N angularly separated light beams, N being the number of prisms in each prism cluster.
This invention relates generally to microstructured optical films, particularly to such films in which the opposed major surfaces are both structured, as well as articles and systems that incorporate such films, and methods pertaining to such films.
BACKGROUNDOptical films that have structured surfaces on opposed major surfaces thereof, referred to herein as dual-sided optical films, are known. In some such films, one structured surface has lenticular features formed therein and the other structured surface has prismatic features formed therein. There is a one-to-one correspondence of prismatic features to lenticular features, and individual prismatic features are elongated and extend parallel to each other and to individual lenticular features, which are also elongated. Such films have been disclosed for use as optical light redirecting films in autostereoscopic 3D display systems. See for example U.S. Pat. No. 8,035,771 (Brott et al.) and U.S. Pat. No. 8,068,187 (Huizinga et al.), and patent application publications US 2005/0052750 (King et al.), US 2011/0149391 (Brott et al.), and US 2012/0236403 (Sykora et al.).
BRIEF SUMMARYWe have developed a new family of dual-sided optical films in which a first structured surface has elongated lenslets formed therein, and a second structured surface, opposed to the first structured surface, has elongated prisms formed therein. The lenslets extend parallel to each other and to an elongation axis which is generally parallel to the film plane, and the prisms also extend parallel to each other and to the elongation axis. The prisms are grouped into separated clusters of adjacent prisms. Each prism cluster is associated with a corresponding one of the lenslets, and has at least 3 prisms. Each lenslet defines a focal point and a focal surface. Vertices of the prisms in a prism cluster are disposed at or near the focal surface of the associated lenslet. For example, a focal space may be defined as a space that encompasses the focal surface and has boundaries that are separated from the focal surface by a differential distance DD equal to 20% of the axial focal length of the lenslet, and the prism vertices of the prisms in the prism cluster associated with the lenslet are disposed in the focal space of the lenslet. When illuminated with oblique light, each lenslet/prism cluster pair, and optionally the optical film as a whole, may produce N angularly separated light beams, N being the number of prisms in each prism cluster.
The present application thus discloses, among other things, optical film that have opposed first and second structured surfaces, the first structured surface having a plurality of elongated lenslets formed thereon, and the second structured surface having a plurality of elongated prisms formed thereon. The plurality of lenslets are elongated along respective lenslet axes which are parallel to an elongation axis, and the elongated prisms have respective elongated prism vertices which are also parallel to the elongation axis. The prisms are grouped into prism clusters that are separated from each other, each prism cluster having at least three of the prisms, and each prism cluster being associated with a corresponding one of the lenslets. Each lenslet defines a focal surface, and for each lenslet, the prism vertices of the prisms in the prism cluster associated with the lenslet are disposed at or near the focal surface. For example, for each lenslet, the lenslet may have an axial focal length, and a focal space encompasses the focal surface and has boundaries that are separated from the focal surface by a differential distance DD equal to 20% of the axial focal length, and the prism vertices of the prisms in the prism cluster associated with the lenslet may be disposed in the focal space of the lenslet. In some cases, for each lenslet, the prism vertices of the prisms in the prism cluster associated with the lenslet may be disposed in a portion of the focal space between the focal surface and the lenslet.
For each lenslet, the prism vertices of the prisms in the prism cluster associated with the lenslet may lie in a plane. For each lenslet, the focal surface may have a first curved shape in a cross-sectional plane perpendicular to the elongation axis. The prism vertices of the prisms in the prism cluster associated with each lenslet may be arranged along a second curved shape in the cross-sectional plane, and the first and second curved shapes may have the same polarity, e.g., both may be concave or both may be convex. Each prism cluster may include 5 of the prisms, or 10 of the prisms. The prism clusters may each contain a same number N of the prisms, where N is at least 3, or at least 5, or at least 10.
For each lenslet, the associated prism cluster may have N of the prisms, and the lenslet may cooperate with its associated prism cluster to provide, when the second structured surface is illuminated with oblique light from a first light source, a first lenslet light output defining N angularly separated light beams, and N may be at least 3. The film may be combined with a diffuser film disposed to receive the first lenslet light output to convert the N angularly separated light beams to one light beam.
The optical film may define a film plane and a thickness axis perpendicular to the film plane, and at least some of the lenslets may have a compound curvature in a cross-sectional plane perpendicular to the elongation axis. Such lenslets may also have respective lenslet axes of symmetry in the cross-sectional plane, and at least some of the lenslet axes of symmetry may be tilted relative to the thickness axis. Similarly, the prisms may have respective prism axes of symmetry in the cross-sectional plane, and at least some of the prism axes of symmetry may be tilted relative to the thickness axis.
The lenslets may be spaced according to a lenslet pitch and the prism clusters may be spaced according to a cluster pitch, and the lenslet pitch may equal the cluster pitch. Alternatively, the lenslet pitch may not equal the cluster pitch. The optical film may be combined with a diffuser film disposed proximate the first structured surface.
We also disclose optical systems in which the dual-sided optical film is combined with a light guide having a major surface adapted to emit light preferentially at oblique angles, and the optical film may be disposed proximate the light guide and oriented so that light emitted from the major surface of the light guide enters the optical film through the second structured surface of the optical film. The system may also include a first and second light source disposed proximate respective first and second opposed ends of the light guide, the first and second light sources providing different respective first and second oblique light beams emitted from the major surface of the light guide. The optical film and the light guide may be non-planar. The optical film and the light guide may be flexible. The optical film may be attached to the light guide.
Related methods, systems, and articles are also discussed.
These and other aspects of the present application will be apparent from the detailed description below. In no event, however, should the above summaries be construed as limitations on the claimed subject matter, which subject matter is defined solely by the attached claims, as may be amended during prosecution.
Inventive aspects of the disclosure may be more completely understood in connection with the accompanying drawings, in which:
The schematic drawings presented herein are not necessarily to scale; however, graphs are assumed to have accurate scales unless otherwise indicated. Like reference numerals used in the figures refer to like elements.
DETAILED DESCRIPTIONAn optical system 100 capable of utilizing the unique properties of the disclosed dual-sided optical films is shown in
The light sources 132, 134 are disposed on opposite ends of the light guide, and inject light into the light guide from opposite directions. Each of the light sources may emit light that is nominally white and of a desired hue or color temperature. Alternatively, each light source may emit colored light, e.g., light perceived to be red, green, blue, or another known non-white color, and/or may emit ultraviolet and/or infrared (including near infrared) light. The light sources may also be or comprise clusters of individual light emitting devices, some or all of which may emit non-white colored light, but the combination of light from the individual devices may produce nominally white light, e.g. from the summation of red, green, and blue light. Light sources on opposite ends of the light guide may emit light of different white or non-white colors, or they may emit light of the same colors. The light sources 132, 134 can be of any known design or type, e.g., one or both may be or comprise cold cathode fluorescent lamps (CCFLs), and one or both may be or comprise one or more inorganic solid state light sources such as light emitting diodes (LEDs) or laser diodes, and one or both may be or comprise one or more organic solid state light sources such as organic light emitting diodes (OLEDs). The round shapes used to represent the light sources in the drawings are merely schematic, and should not be construed to exclude LED(s), or any other suitable type of light source. The light sources 132, 134 are preferably electronically controllable such that either one can be energized to an ON state (producing maximum or otherwise significant light output) while keeping the other one in an OFF state (producing little or no light output), or both can be in the ON state at the same time if desired, and both may be turned OFF during non-use. In many cases, the light sources 132, 134 do not need to satisfy any particular requirement with regard to switching speed. For example, although either or both light sources 132, 134 may be capable of repetitively transitioning between the OFF state and the ON state at a rate that is imperceptible to the human eye (e.g., at least 30 or 60 Hz), such a capability is not necessary in many embodiments. (For flicker-free operation, transition rates may be in a range from 50 to 70 Hz, or more; for two-sided operation, transition rates may be in a range from 100 to 140 Hz (or more) for the display panel (if any) and the light sources.) Thus, light sources that have much slower characteristic transition times between the ON and OFF states can also be used.
The light guide 150 includes a first light input side 150c adjacent to the first light source 134 and an opposing second light input side 150d adjacent to the second light source 132. A first light guide major surface 150b extends between the first side 150c and second side 150d. A second light guide major surface 150a, opposite the first major surface 150b, also extends between the first side 150c and the second side 150d. The major surfaces 150b, 150a of the light guide 150 may be substantially parallel to each other, or they may be non-parallel such that the light guide 150 is wedge-shaped. Light may be reflected or emitted from either surface 150b, 150a of the light guide 150, but in general light is emitted from surface 150a and is reflected from surface 150b. In some cases, a highly reflective surface may be provided on or adjacent to the first surface 150b to assist in re-directing light out through the second surface 150a. Light extraction features such as shallow prism structures 152, or other light extraction features such as lenticular features, white dots, haze coatings, and/or other features, may be disposed on one or both major surfaces 150b, 150a of the light guide 150. Exemplary light extraction features for the light guide are discussed below in connection with
The light guide 150 may have a solid form, i.e., it may have an entirely solid interior between the first and second major surfaces 150a, 150b. The solid material may be or comprise any suitable light-transmissive material, such as glass, acrylic, polyester, or other suitable polymer or non-polymer materials. Alternatively, the light guide 150 may be hollow, i.e., its interior may be air or another gas, or vacuum. If hollow, the light guide 150 is provided with optical films or similar components on opposite sides thereof to provide the first and second major surfaces 150a, 150b. Hollow light guides may also be partitioned or subdivided into multiple light guides. Whether solid or hollow, the light guide 150 may be substantially planar, or it may be non-planar, e.g., undulating or curved, and the curvature may be slight (close to planar) or great, including cases where the light guide curves in on itself to form a complete or partial tube. Such tubes may have any desired cross-sectional shape, including curved shapes such as a circle or ellipse, or polygonal shapes such as a square, rectangle, or triangle, or combinations of any such shapes, A hollow tubular light guide may in this regard be made from a single piece of optical film or similar component(s) that turns in on itself to form a hollow tube, in which case the first and second major surfaces of the light guide may both be construed to be provided by such optical film or component(s). The curvature may be only in the x-z plane, or only in the y-z plane, or in both planes. Although the light guide and dual-sided film may be non-planar, for simplicity they are shown in the figures as being planar; in the former case one may interpret the figures as showing a small enough portion of the light guide and/or optical film such that it appears to be planar. Whether solid or hollow, depending on the material(s) of construction and their respective thicknesses, the light guide may be physically rigid, or it may be flexible. A flexible light guide or optical film may be flexed or otherwise manipulated to change its shape from planar to curved or vice versa, or from curved in one plane to curved in an orthogonal plane.
The dual-sided optical film 140, which is assumed to lie in or define a film plane generally parallel to the x-y plane, is disposed to receive obliquely-emitted light from the light guide 150. The film 140 has a first structured surface 140a, and a second structured surface 140b opposite the first structured surface. Elongated lenslets 144 are formed in the structured surface 140a, which is oriented generally away from the light guide 150.
Elongated prisms (shown better in figures that follow) are formed in the second structured surface 140b, which is oriented generally towards the light guide 150. In this orientation, light emitted from the major surface 150a of the light guide 150 is incident on the prisms, which help to deviate the incident light. The incident light is deviated by and passes through the film 140 to provide a film light output that emerges from the film 140. As described further below, the properties of the film light output can be influenced by which of the light sources 132, 134 is in an ON state, as well as by the spatial relationships between the lenslets and the prisms. When one light source is ON, a first film light output may comprise a first group of N angularly separated light beams. When the opposite light source is ON, a second film light output may comprise a second group of N angularly separated light beams, which beams may be substantially aligned with, or not aligned with, the first group of light beams. As shown better in other figures below, the prisms are grouped into clusters of adjacent prisms, the clusters being separated from each other, and each prism cluster being associated with a corresponding one of the lenslets. These prisms have sharp apexes so as to provide beam edges, measured e.g. from a plot of intensity versus angle, that are sharp.
Both the prisms and the lenslets 144 are typically linear, or, in cases where one or both are not precisely linear (e.g. not straight), they are otherwise extended or elongated along a particular in-plane axis. Thus, the lenslets 144 may extend along lenslet axes that are parallel to each other. One such axis is shown in
In the film 140 or pertinent portion thereof, there is a one-to-one correspondence of lenslets 144 to prism clusters. Thus, for each prism cluster there is a unique lenslet 144 with which the given prism cluster primarily interacts, and vice versa. One, some, or all of the lenslets 144 may be in substantial registration with their respective prism clusters. Alternatively, the film 140 may be designed to incorporate a deliberate misalignment or mis-registration of some or all of the lenslets relative to their respective prism clusters. Related to alignment or misalignment of the lenslets and prism clusters is the center-to-center spacings or pitches of these elements. In the case of a display system, the pitch of the lenslets 144 and the pitch of the prism clusters (as well as the pitch of the individual prisms in the prism clusters) may be selected to reduce or eliminate Moire patterns with respect to periodic features in the display panel. These various pitch dimensions can also be determined or selected based upon manufacturability. Useful pitch ranges for the lenslets 144 and the prism clusters on the respective structured surfaces of the optical film 140 is about 10 microns to about 140 microns, for example, but this should not be interpreted in an unduly limiting way.
The system 100 can have any useful shape or configuration. In many embodiments, the light guide 150, and/or the dual-sided optical film 140 can have a square or rectangular shape. In some embodiments, however, any or all of these elements may have more than four sides and/or a curved shape.
A switchable driving element 160 is electrically connected to the first and second light sources 132, 134. This element may contain a suitable electrical power supply, e.g. one or more voltage sources and/or current sources, capable of energizing one or both of the light sources 132, 134. The power supply may be a single power supply module or element, or a group or network of power supply elements, e.g., one power supply element for each light source. The driving element 160 may also contain a switch that is coupled to the power supply and to the electrical supply lines that connect to the light sources. The switch may be a single transistor or other switching element, or a group or network of switching modules or elements. The switch and power supply within the driving element 160 may be configured to have several operational modes. These modes may include two, three, or all of: a mode in which only the first light source 134 is ON; a mode in which only the second light source 132 is ON; a mode in which both the first and second light sources are ON; and a mode in which neither of the first and second light sources are ON (i.e., both are OFF).
We describe in more detail below how the dual-sided optical film 140, when provided with separated clusters of adjacent prisms, can provide the optical system with the capability to produce a light output characterized by a group of light beams that are closely spaced but separated from each other in output angle. The group of beams has sharp edges at two opposite boundaries of the beams, and the individual beams may also have sharp edges. The characteristics and features of the light output are controlled by design details of the lenslets and prism clusters, as explained further below.
The disclosed dual-sided optical films and associated components may be provided in a variety of forms and configurations. In some cases, the dual-sided optical film may be packaged, sold, or used by itself, e.g. in piece, sheet, or roll form. In other cases, the dual-sided optical film may be packaged, sold, or used with a light guide whose output beam characteristics are tailored for use with the dual-sided film. In such cases, the dual-sided film may be bonded to the light guide as discussed above, or they may not be bonded to each other. In some cases, the dual-sided optical film may be packaged, sold, or used with both a light guide that is tailored for use with the dual-sided film, and one or more LED(s) or other light source(s) that are adapted to inject light into the light guide, e.g., from opposite ends thereof as shown generally in
The rear major surface 250b of the light guide is preferably machined, molded, or otherwise formed to provide a linear array of shallow prism structures 252. These prism structures are elongated along axes parallel to the y-axis, and are designed to reflect an appropriate portion of the light propagating along the length of the light guide (along the x-axis) so that the reflected light can refract out of the front major surface 250a into air (or a tangible material of suitably low refractive index) at a suitably oblique angle, and onward to the dual-sided optical film. In many cases, it is desirable for the reflected light to be extracted from the front major surface 250a relatively uniformly along the length of the light guide 250. The surface 250b may be coated with a reflective film such as aluminum, or it may have no such reflective coating. In the absence of any such reflective coating, a separate back reflector may be provided proximate the surface 250b to reflect any downward-propagating light that passes through the light guide so that such light is reflected back into and through the light guide. The prism structures 252 typically have a depth that is shallow relative to the overall thickness of the light guide, and a width or pitch that is small relative to the length of the light guide. The prism structures 252 have apex angles that are typically much greater than the apex angles of prisms used in the disclosed dual-sided optical films. The light guide may be made of any transparent optical material, typically with low scattering such as polycarbonate, or an acrylic polymer such as Spartech Polycast material. In one exemplary embodiment, the light guide may be made of acrylic material, such as cell-cast acrylic, and may have an overall thickness of 1.4 mm and a length of 140 mm along the x-axis, and the prisms may have a depth of 2.9 micrometers and a width of 81.6 micrometers, corresponding to a prism apex angle of about 172 degrees. The reader will understand that these values are merely exemplary, and should not be construed as unduly limiting.
The front major surface 250a of the light guide may be machined, molded, or otherwise formed to provide a linear array of lenticular structures or features 254 that are parallel to each other and to a lenticular elongation axis. In contrast to the elongation axis of the prism structures 252, the lenticular elongation axis is typically parallel to the x-axis. The lenticular structures 254 may be shaped and oriented to enhance angular spreading in the y-z plane for light that passes out of the light guide through the front major surface, and, if desired, to limit spatial spreading along the y-axis for light that remains in the light guide by reflection from the front major surface. In some cases, the lenticular structures 254 may have a depth that is shallow relative to the overall thickness of the light guide, and a width or pitch that is small relative to the width of the light guide. In some cases, the lenticular structures may be relatively strongly curved, while in other cases they may be more weakly curved. In one embodiment, the light guide may be made of cell-cast acrylic and may have an overall thickness of 0.76 mm, a length of 141 mm along the x-axis, and a width of 66 mm along the y-axis, and the lenticular structures 254 may each have a radius of 35.6 micrometers, a depth of 32.8 micrometers, and a width 323 of 72.6 mm, for example. In this embodiment, the prism structures 252 may have a depth of 2.9 micrometers, a width of 81.6 micrometers, and a prism apex angle of about 172 degrees. Again, the reader will understand that these embodiments are merely exemplary, and should not be construed as unduly limiting; for example, structures other than lenticular structures may be used on the front major surface of the light guide.
As mentioned above, the lenticular structures 254 may be shaped and oriented to limit spatial spreading along the y-axis for light that remains in the light guide by reflection from the front major surface. Limited spatial spreading along the y-axis can also be achieved, or enhanced, with light sources that are collimated (including substantially collimated) in the plane of the light guide, i.e., the x-y plane. Such a light source may be a relatively small area LED die or dies in combination with one or more collimating lenses, mirrors, or the like.
Turning now to
Light from the energized light source 134 enters the light guide 150 through the first side 150c. This light travels along the light guide 150 generally in the positive x-direction, the light reflecting from the major surfaces 150a, 150b to provide a first guided light beam 134-1. As the beam 134-1 propagates, some of the light is refracted or otherwise extracted from the major surface 150a to provide an oblique light beam 134-2, represented by obliquely oriented arrows representing a direction of maximum light intensity in the x-z plane. The oblique light beam 134-2 is typically emitted over substantially the entire surface area of the major surface 150a, i.e., not only in the geometric center of the major surface 150a but also at or near its edges and at intermediate positions in between, as indicated by the multiple oblique arrows. The oblique light beam 134-2 has a direction of maximum light intensity that is most closely aligned with the positive x-direction. The direction of maximum light intensity of the beam 134-2 may deviate from the positive x-direction by, for example, 30 degrees or less, or 20 degrees or less, or 15 degrees or less, or 10 degrees or less.
Because of the directionality of the oblique light beam 134-2, light from the light source 134 may enter the dual-sided optical film 140 predominantly through only one inclined side surface of each of the prisms on the second structured surface 140b of the film 140. Refraction provided at such inclined surfaces, in cooperation with reflection provided at other inclined surfaces of the prisms, and in cooperation with refraction provided by the lenslets 144, causes light to emerge from the film 140 as the first film light output 310. The first film light output 310 arises from the summation of individual light outputs emitted from each lenslet 144 across the film 140, which individual outputs are referred to as lenslet light outputs. For simplicity, we assume that the film 140 is configured such that the individual lenslet light outputs have angular distributions that are the same as each other, and the same as that of the film light output 310. In other embodiments, the angular distributions of the individual lenslet light outputs may differ from each other, and which would then sum together to provide an overall film light output that has a different angular distribution from that of the individual lenslet light outputs.
If the first light source 134 is turned OFF and the second light source 132 is turned ON, the system 100 produces a second film light output, which is also characterized by a generally fan-shaped angular distribution in the x-z plane which is or includes a group of closely spaced (as a function of angle θ) but angularly separated lobes, the outermost lobes defining sharp transitions at the outer opposite edges or sides of the light output. Depending upon the amount of fluctuation between the lobe peaks and the relative minima between lobes, some or all of the lobes may be considered to be separate light beams. The second film light output typically covers an angular range that differs from that of the first film light output, but the angular distributions of these two film light outputs typically overlap, whether or not any of their respective individual lobes (or beams) overlap.
Thus, in
Light from the energized light source 132 enters the light guide 150 through the second side 150d. This light travels along the light guide 150 generally in the negative x-direction, the light reflecting from the major surfaces 150a, 150b to provide a first guided light beam 132-1. As the beam 132-1 propagates, some of the light is refracted or otherwise extracted from the major surface 150a to provide an oblique light beam 132-2, represented by obliquely oriented arrows representing a direction of maximum light intensity in the x-z plane. The oblique light beam 132-2 is typically emitted over substantially the entire surface area of the major surface 150a, i.e., not only in the geometric center of the major surface 150a but also at or near its edges and at intermediate positions in between, as indicated by the multiple oblique arrows. The oblique light beam 132-2 has a direction of maximum light intensity that is most closely aligned with the negative x-direction. The direction of maximum light intensity of the beam 132-2 may deviate from the negative x-direction by, for example, 30 degrees or less, or 20 degrees or less, or 15 degrees or less, or 10 degrees or less.
Because of the directionality of the oblique light beam 132-2, light from the light source 132 may enter the dual-sided optical film 140 predominantly through only a second inclined side surface of each of the prisms on the second structured surface 140b of the film 140, this second inclined surface being the opposite of the inclined surface used in connection with
We will now discuss design details of exemplary dual-sided optical films that allow the films to produce light outputs, such as those shown in
The structured surfaces of the films can be made using any known microreplication techniques, e.g. by embossing or thermoforming a polymer film, or using continuous cast-and-cure methods. In the latter case, a curable polymer material or polymer precursor material may be applied between a transparent carrier film and a suitably configured structured surface tool. The material is then cured and separated from the tool to provide a layer that is bonded to the carrier film and has the desired microstructured topography. One such layer can be applied on one side of the carrier film to form the lenslets (see e.g. the first structured surface 140a in
The structured surfaces of the disclosed dual-sided optical films, as well as the structured surfaces of the disclosed light guides, can alternatively or in addition be made using known additive manufacturing techniques, sometimes referred to as three-dimensional printing or 3D printing.
The first structured surface 540a has a plurality of lenslets 544 formed therein. Each of these lenslets 544 extends along an elongation axis that is parallel to the y-axis. The lenslets 544 may have a single, uniform curvature, i.e. the curved surface of each lenslet may be a portion of a right circular cylinder, or they may have a non-uniform curvature, e.g., a continuously variable curvature with a smaller radius of curvature in a central portion and greater radius of curvature near the edges, or vice versa. A lenslet that has a non-uniform curvature is said to have a compound curvature. Each lenslet 544 also has a vertex, labeled V. Whether the lenslet 544 has a compound curvature or a simple (uniform) curvature, the curvature of the lenslet 544 at its vertex V may be characterized by a center of curvature, which is labeled C in
The second structured surface 540b has a plurality of prisms 541 formed therein. Similar to the lenslets 544, the prisms 541 each extend along an elongation axis parallel to the y-axis. Each prism 541 has two inclined side surfaces, which meet at a sharp peak or vertex of the prism, labeled Vprism. The included angle of each prism 541 at its vertex, referred to as a vertex angle, is typically in a range from 50 to 90 degrees, e.g., 63.5 degrees, but this should not be construed as unduly limiting. Regardless of the vertex angle, the vertex is desirably sharp rather than truncated or rounded, e.g., having a radius of curvature of no more than 3 microns, or no more than 2 microns, or no more than 1 micron, or less. The prism vertex may in this regard be described as dead sharp. The prisms 541 do not occupy the entire second structured surface 540b, but are organized into groups or clusters 543 of adjacent prisms 541, which clusters 543 are separated from each other by one or more features that do not include elongated prisms. In the embodiment of
There is a one-to-one correspondence of lenslets 544 to prism clusters 543. For a given lenslet 544, one of the prism clusters 543 predominantly interacts optically with (and typically is closest to) the lenslet, thus, the lenslet 544 and the prism cluster 543 associated with it in this manner can be said to form a lenslet/prism cluster pair 548. Two such complete pairs 548 are shown in
In describing the configuration and design of the disclosed dual-sided films, it is useful to assign to each prism cluster a representative feature that is located centrally within the group of individual prisms that make up the cluster. The most relevant such representative feature is the prism vertex Vprism for the prism that is centrally located within the prism cluster, e.g., equal numbers of the remaining prisms in the cluster are located on opposite sides of the central prism. If no prism is centrally located, the representative feature of the cluster can be taken to be the prism vertex Vprism for the prism that is most nearly centrally located within the prism cluster. In the embodiment of
Turning now to
It is useful to define, for each lenslet 544, a region of space or volume in proximity to the focal surface 552 of the lenslet, which we refer to as a focal space. We begin by identifying the axial focal length of the lenslet 544, which is measured from the vertex V of the lenslet to the focal point f along the optical axis 525. This axial focal length is labeled D in
An enlarged view of this focal space 555 is shown in
Due to the enlarged view of
Turning now to
The first structured surface 640a has a plurality of lenslets 644 formed therein. Each lenslet 644 extends along an elongation axis that is parallel to the y-axis. The lenslets 644 may have a single, uniform curvature, or they may have a compound curvature. Each lenslet 644 also has a vertex V. The curvature of the lenslet 644 at its vertex V may be characterized by a center of curvature, labeled C. The vertex V and the center of curvature C for each lenslet 644 lie on an axis 625, similar to the axis 525 from
The second structured surface 640b has a plurality of prisms 641 formed therein. Similar to the lenslets 644, the prisms 641 each extend along an elongation axis parallel to the y-axis. Each prism 641 has two inclined side surfaces, which meet at a sharp peak or vertex Vprism. Details of the prism vertices are discussed elsewhere herein.
The prisms 641 are organized into groups or clusters 643 of adjacent prisms 641, which are separated from each other by one or more features that do not include elongated prisms. In the embodiment of
One difference between the film 640 and the film 540 is that in the film 640, the prism vertices Vprism in a given prism cluster 643 do not lie in a common plane, unlike the prism vertices in a prism cluster 543. In the film 640, the prism vertices in a given cluster 643 lie along a curved path, as discussed below in connection with
The prism clusters 643 are characterized by a centrally located prism vertex, which is referred to as the cluster vertex and labeled Vcluster, just as in
In
Each prism 641 has a vertex angle θinc, which is typically the same for all the prisms in the cluster 643, and for the prisms of other prism clusters on the second structured surface. Bisecting each vertex angle θinc is a prism axis PA, which can be considered to be an optical axis of a given prism 641. In the embodiment of
Depending on details of construction, the film 640 of
The film 740 has opposed first and second structured surfaces 740a, 740b, and is shown in relation to a Cartesian x-y-z coordinate system consistent with the previous figures. The first structured surface 740a has a plurality of lenslets 744 formed therein. Each lenslet 744 extends along an elongation axis that is parallel to the y-axis. The lenslets 744 may have a single, uniform curvature, or they may have a compound curvature. Each lenslet 744 also has a vertex V. The curvature of the lenslet 744 at its vertex V may be characterized by a center of curvature C. The vertex V and the center of curvature C for each lenslet 744 lie on an axis 725. The lenslets 744 may collectively be characterized by a pitch P1 (see e.g.
The second structured surface 740b has a plurality of prisms 741 formed therein. The prisms 741 each extend along an elongation axis parallel to the y-axis. Each prism 741 has two inclined side surfaces, which meet at a sharp peak or vertex Vprism. The prisms 741 are organized into groups or clusters 743 of adjacent prisms 741, which are separated from each other by one or more features that do not include elongated prisms. There is a one-to-one correspondence of lenslets 744 to prism clusters 743. For a given lenslet 744, one of the prism clusters 743 predominantly interacts optically with and is typically closest to the lenslet, thus, the lenslet 744 and the prism cluster 743 associated with it in this manner form a lenslet/prism cluster pair 748. Two such complete pairs 748 are shown in
Design aspects of films discussed elsewhere herein can also be applied to the film 740 of
The film 840 has opposed first and second structured surfaces 840a, 840b, and is shown in relation to a Cartesian x-y-z coordinate system consistent with the previous figures. The first structured surface 840a has a plurality of lenslets 844 formed therein. Each lenslet 844 extends along an elongation axis that is parallel to the y-axis. The lenslets 844 may have a single, uniform curvature, or they may have a compound curvature. Each lenslet 844 also has a vertex V. The curvature of the lenslet 844 at its vertex V may be characterized by a center of curvature C. The vertex V and the center of curvature C for each lenslet 844 lie on an axis 825. The lenslets 844 may collectively be characterized by a pitch P1 (see e.g.
The second structured surface 840b has a plurality of prisms 841 formed therein. The prisms 841 each extend along an elongation axis parallel to the y-axis. Each prism 841 has two inclined side surfaces, which meet at a sharp peak or vertex Vprism. The prisms 841 are organized into groups or clusters 843 of adjacent prisms 841, which are separated from each other by one or more features that do not include elongated prisms. There is a one-to-one correspondence of lenslets 844 to prism clusters 843. For a given lenslet 844, one of the prism clusters 843 predominantly interacts optically with and is typically closest to the lenslet, thus, the lenslet 844 and the prism cluster 843 associated with it in this manner form a lenslet/prism cluster pair 848. Two such complete pairs 848 are shown in
Design aspects of films discussed elsewhere herein can also be applied to the film 840 of
In
The second structured surface 940b of the film 940 comprises a plurality of prisms (not shown in this schematic view), each of which extends along an elongation axis parallel to the y-axis. Each of these prisms has a sharp peak or vertex which is also not shown in this schematic view. The prisms are organized into groups or clusters 943 of adjacent prisms, which are separated from each other by one or more features that do not include elongated prisms, e.g., a flat surface, a large V-groove, or other suitable surface shapes. For generality, the prism clusters 943 are shown only schematically in
Not only do the lenslets 944 and prism clusters 943 have the same pitch, but they are also in alignment with each other along the z-axis or thickness axis of the film 940. That is, for a given lenslet/prism cluster pair 948, the vertex V of the lenslet and the central feature Vcluster of the prism cluster have the same x-coordinate but different z-coordinates. Therefore, each lenslet/prism cluster pair 948 has an optical axis that is parallel to the z-axis. Assuming the lenslets 944 are of the same design and the prism clusters 943 are also of the same design, the lenslet/prism cluster pairs 948 will thus be substantially the same or similar to each other (except for a translation along the x-axis), and will produce lenslet light outputs whose angular distributions are also substantially the same or similar. These lenslet light outputs will then sum together to provide an overall film light output for the film 940 whose angular distribution is substantially the same as, or similar to, those of the individual lenslet light outputs. Depending on design details of the lenslets, prisms, and prism clusters, the lenslet light outputs and the film light output may define N angularly separated lobes or beams when oblique light illuminates the second structured surface 940b of the film, similar to the light output shown in
The dual-sided optical film 1040 of
The second structured surface 1040b of the film 1040 comprises a plurality of prisms (not shown in this schematic view), each of which extends along an elongation axis parallel to the y-axis. Each of these prisms has a sharp peak or vertex which is also not shown in this schematic view. The prisms are organized into groups or clusters 1043 of adjacent prisms, which are separated from each other by one or more features that do not include elongated prisms, e.g., a flat surface, a large V-groove, or other suitable surface shapes. For generality, the prism clusters 1043 are shown only schematically in
Since the lenslets 1044 and prism clusters 1043 have different pitches, many of them are in misalignment or misregistration with each other along the z-axis or thickness axis of the film 1040. That is, for most of the lenslet/prism cluster pairs 1048, the vertex V of the lenslet and the central feature Vcluster of the prism cluster have the different x-coordinates (as well as different z-coordinates). In the depicted embodiment, the lenslet/prism cluster pair 1048 that is located centrally within the film 1040 is assumed to have a lenslet 1044 in registration with is associated prism cluster 1043; for lenslet/prism cluster pairs 1048 that are located progressively farther away from the center of the film 1040 (and closer to the edges of the film 1040), the lenslets and prism clusters become progressively more misaligned with each other. Thus, the optical axis of the centrally located lenslet/prism cluster pair is parallel to the z-axis, but the optical axes of the other lenslet/prism cluster pairs are not, and are tilted with respect to the z-axis at angles whose magnitudes progressively increase with increasing distance from the center of the film 1040. This is shown in
Assuming the lenslets 1044 are of the same design and the prism clusters 1043 are also of the same design, the lenslet/prism cluster pairs 1048 will thus be similar to each other except for the progressive misalignment discussed above, and will produce lenslet light outputs whose angular distributions are shifted in angle with respect to each other. These lenslet light outputs will then sum together to provide an overall film light output for the film 1040, as indicated schematically in
For any given lenslet/prism cluster pair, but particularly for those whose optical axes are tilted with respect to the z-axis, it may be desirable for the lenslet to have an axis of symmetry or optical axis that is tilted commensurately with respect to the z-axis, as well as prisms whose individual axes of symmetry or prism axes PA are also commensurately tilted with respect to the z-axis.
A lenslet that has a compound curvature rather than a simple curvature, when designed symmetrically, has a single, well-defined symmetry axis or optical axis. Such a lenslet 1112 is shown schematically in
A schematic view of a generalized lenslet/prism cluster pair 1248 that may be present in any of the disclosed dual-sided optical films is shown in
The lenslet 1244 is assumed to be tilted and, as such, the simple lenslet vertex V that was shown in some of the previous figures such as
The prism cluster 1243 is shown to have five individual prisms 1241, but the reader will understand the other numbers of (at least three) prisms may also be used. The prisms 1241 all have sharp vertices Vprism. The vertex of the prism that is centrally located within the cluster 1243 is designated the cluster vertex, Vcluster. Each prism 1241 also has a prism axis PA which bisects the vertex angle θinc of the prism. In this embodiment, the vertex angles of the prisms 1241 are assumed to be the same or similar, but the prisms 1241 are assumed to be tilted by different amounts relative to the z-axis, as exemplified by the different tilt angles of their prism axes PAa, PAb, PAc, PAd, and PAe relative to the z-axis. (In alternative embodiments, the prisms in a given cluster may all be tilted by the same amount, while prisms in different clusters may be tilted by different amounts.) The tilt of the prism cluster 1243 as a whole may be characterized best by the tilt of the centrally located prism, i.e., by the tilt of the prism axis PAc.
By appropriate selection of film thicknesses and/or coating thicknesses, the vertical distance Dz between the cluster vertex Vcluster and the lenslet symmetry vertex SV can be controlled to provide desired optical performance of the light output, also taking into consideration the refractive index of the optical film. The lenslet 1244 is translationally misaligned with the prism cluster 1243, as represented by its centrally located prism, by a displacement amount Dx along the x-axis. The lenslet 1244 is also rotationally misaligned with the prism cluster 1243: the lenslet optical axis 1225 is tilted in the x-z plane with respect to the prism axis PAc, and furthermore, both the lenslet optical axis 1225 and the prism axis PAc are tilted with respect to the z-axis. The angles α and β can be used to refer to the tilt angles of the lenslet optical axis and the central prism axis, as shown in the figure. The dual-sided optical films disclosed herein can make appropriate use of the design parameters Dz, Dx, α, and β, which may be uniform over the area of the film (for all lenslet/prism cluster pairs) or which may be non-uniform over such area. These parameters may be used to tailor lenslet light outputs and/or film light outputs as desired, such light outputs being provided when only one of two light sources is ON, or when only the other light source is ON, or when both such light sources are ON.
Dual-sided optical films that employ tilting of the prisms and/or lenslets as shown in
Lenslets 1344 are formed in the first structured surface 1340a, each lenslet having a vertex V as well as a focal point, a focal surface, and a focal space as described generally above. Each lenslet 1344 extends linearly along the y-axis, and has a compound curvature in the x-z plane with a mean radius of curvature of 37.3 microns, and a radius of curvature at the vertex V of 35.4 microns. The compound curvature was tailored to minimize spherical aberration at the focal point of the lenslet. The optical axis of each lenslet 1344 has a zero tilt with respect to the z-axis. The maximum thickness of the layer 1346, i.e., the physical thickness of the layer 1346 as measured at any of the lenslet vertices V, is 15 microns. The pitch of the lenslets 1344 is 50 microns.
A plurality of prisms 1341 are formed in the second structured surface 1340b. The prisms 1341 each extend linearly along an elongation axis parallel to the y-axis. Each prism 1341 has two inclined side surfaces, which meet at a sharp peak or vertex Vprism, not labeled in
The overall thickness or caliper of the film 1340, i.e., the physical distance from a given lenslet vertex V to its corresponding cluster vertex Vcluster, is 111 microns.
Different types of oblique light were then injected into the film 1340 to simulate a light guide emitting light into the second structured surface 1340b. A first oblique input light, referred to here as a left input distribution, had an angular distribution that was Gaussian, with a maximum intensity at an angle of 70 degrees from the z-axis with a positive x-component, and a full-width-at-half-maximum of 20 degrees.
Additional dual-sided optical films were also modeled and evaluated by optical simulation.
Lenslets 1444 are formed in the first structured surface 1440a, each lenslet having a vertex V as well as a focal point, a focal surface, and a focal space as described generally above. Each lenslet 1444 extends linearly along the y-axis, and has a simple curvature in the x-z plane with a constant radius of curvature of 34.5 microns. The maximum thickness of the layer 1446, i.e., the physical thickness of the layer 1446 as measured at any of the lenslet vertices V, is 15 microns. The pitch P1 of the lenslets 1444 is 44 microns.
A plurality of prisms 1441 are formed in the second structured surface 1440b. The prisms 1441 each extend linearly along an elongation axis parallel to the y-axis. Each prism 1441 has two inclined side surfaces, which meet at a sharp peak or vertex. The prisms 1441 each have a prism angle θinc of 60 degrees, and prism axes that bisect such angles. The prisms 1441 are organized into clusters 1443 of 7 adjacent prisms 1441, which clusters are separated from each other by large individual V-grooves 1420. There is a one-to-one correspondence of lenslets 1444 to prism clusters 1443, associated ones of which form lenslet/prism cluster pairs 1448. Although only 5 complete pairs 1448 are shown in the figure, the film 1440 as modeled had exactly 21 such pairs 1448. The vertex of the prism 1441 located centrally within each cluster 1443 serves as the cluster vertex Vcluster. This centrally located prism, as well as the six other prisms 1441 in the cluster, all have zero tilt with respect to the z-axis. The prism vertices in a given cluster 1443 are all located in the focal space of the associated lenslet 1444, where the focal space is defined in the same way as the focal space 555 discussed above. The prism vertices in a given cluster 1443 are coplanar. The pitch P3 of the prisms 1441 is 4 microns, and the pitch P2 of the prism clusters 1443 is 44 microns, i.e., the same as the pitch of the lenslets 1344. Besides having the same pitch, the prism clusters 1443 and the lenslets 1444 are also aligned or registered with respect to each other, such that the optical axis of each lenslet/prism cluster pair 1448 is parallel to the z-axis.
The overall thickness or caliper D of the film 1440, i.e., the physical distance from a given lenslet vertex V to its corresponding cluster vertex Vcluster, is 101 microns.
An oblique input light was then injected into the film 1440 to simulate a light guide emitting light into the second structured surface 1440b. The input light was the sum of two Gaussian distributions, one of which had an angular distribution with a maximum intensity at an angle of 70 degrees from the z-axis with a positive x-component, and a full-width-at-half-maximum of 20 degrees, and the other of which had an angular distribution with a maximum intensity at an angle of 70 degrees from the z-axis with a negative x-component, and the same full-width-at-half-maximum.
Another dual-sided optical film that was modeled and evaluated by optical simulation is shown in
The film 1540 thus has opposed first and second structured surfaces 1540a, 1540b, respectively, and a 3-layer construction, with a central layer 1547 of uniform thickness, representing a carrier film, and outer layers 1545, 1546 attached thereto and having the relevant structured surfaces, as shown. The layers 1545, 1546, and 1547 have the same refractive indices as the corresponding layers of the film 1440, and the layer 1547 has the same thickness as the layer 1447.
Lenslets 1544 are formed in the first structured surface 1540a, each lenslet having a vertex V as well as a focal point, a focal surface, and a focal space, which are all the same as corresponding features of the lenslets 1444, the lenslets 1544 also extending linearly along the y-axis, and having a simple curvature in the x-z plane with the same constant radius of curvature as lenslets 1444. The maximum thickness of the layer 1546 is the same as that of layer 1446, and the pitch P1 of the lenslets 1544 is the same as that of lenslets 1444.
A plurality of prisms 1541 are formed in the second structured surface 1540b. The prisms 1541 each extend linearly along an elongation axis parallel to the y-axis, and the two inclined side surfaces of each prism meet at a sharp peak or vertex. The prisms 1541 have the same prism angle θinc as that of prisms 1441, and are organized into clusters 1543 of 7 adjacent prisms 1541, which clusters are separated from each other by large individual V-grooves 1520. There is a one-to-one correspondence of lenslets 1544 to prism clusters 1543, associated ones of which form lenslet/prism cluster pairs 1548. The film 1540 as modeled had exactly 21 complete pairs 1548. The vertex of the prism 1541 located centrally within each cluster 1543 serves as the cluster vertex Vcluster. This centrally located prism, as well as the six other prisms 1541 in the cluster, all have zero tilt with respect to the z-axis. The prism vertices in a given cluster 1543 are all located in the focal space of the associated lenslet 1544, where the focal space is defined in the same way as the focal space 555 discussed above. The prism vertices in a given cluster 1543 are coplanar. The pitch P3 of the prisms 1541, and the pitch P2 of the prism clusters 1543, is the same as the corresponding pitches of the film 1440, and the prism clusters 1543 and the lenslets 1544 are also aligned or registered with respect to each other.
The overall thickness or caliper D of the film 1540 was reduced relative to the corresponding dimension of the film 1440 by 15 microns, which had the effect of positioning the cluster vertex Vcluster a distance of 15 microns from the focal point of the lenslet 1540, between the focal point and the lenslet.
The same oblique input light used in connection with the film 1440 was then injected into the second structured surface 1540b of the film 1540.
Another dual-sided optical film that was modeled and evaluated by optical simulation is shown in
The film 1640 thus has opposed first and second structured surfaces 1640a, 1640b, respectively, and a 3-layer construction, with a central layer 1647 of uniform thickness, representing a carrier film, and outer layers 1645, 1646 attached thereto and having the relevant structured surfaces, as shown. The layers 1645, 1646, and 1647 have the same refractive indices as the corresponding layers of the film 1540, and the layer 1647 has the same thickness as the layer 1547.
Lenslets 1644 are formed in the first structured surface 1640a, each lenslet having a vertex V as well as a focal point, a focal surface, and a focal space, which are all the same as corresponding features of the lenslets 1544, the lenslets 1644 also extending linearly along the y-axis, and having a simple curvature in the x-z plane with the same constant radius of curvature as lenslets 1544. The maximum thickness of the layer 1646 is the same as that of layer 1546, and the pitch P1 of the lenslets 1644 is the same as that of lenslets 1544.
A plurality of prisms 1641 are formed in the second structured surface 1640b. The prisms 1641 each extend linearly along an elongation axis parallel to the y-axis, and the two inclined side surfaces of each prism meet at a sharp peak or vertex. The prisms 1641 have the same prism angle θinc as that of prisms 1541, and are organized into clusters 1643 of 7 adjacent prisms 1641. Rather than being separated from each other by large individual V-grooves, the clusters 1643 are separated by flat surfaces 1621. There is a one-to-one correspondence of lenslets 1644 to prism clusters 1643, associated ones of which form lenslet/prism cluster pairs 1648. The film 1640 as modeled had exactly 21 complete pairs 1648. The vertex of the prism 1641 located centrally within each cluster 1643 serves as the cluster vertex Vcluster. This centrally located prism, as well as the six other prisms 1641 in the cluster, all have zero tilt with respect to the z-axis. The prism vertices in a given cluster 1643 are all located in the focal space of the associated lenslet 1644, where the focal space is defined in the same way as the focal space 555 discussed above. The prism vertices in a given cluster 1643 are coplanar. The pitch P3 of the prisms 1641, and the pitch P2 of the prism clusters 1643, is the same as the corresponding pitches of the film 1540, and the prism clusters 1643 and the lenslets 1644 are also aligned or registered with respect to each other.
The overall thickness or caliper D of the film 1640 was the same as the corresponding dimension of the film 1540.
The same oblique input light used in connection with the film 1540 was then injected into the second structured surface 1640b of the film 1640.
Another dual-sided optical film that was modeled and evaluated by optical simulation is shown in
The film 1740 thus has opposed first and second structured surfaces 1740a, 1740b, respectively, and a 3-layer construction, with a central layer 1747 of uniform thickness, representing a carrier film, and outer layers 1745, 1746 attached thereto and having the relevant structured surfaces, as shown. The layers 1745, 1746, and 1747 have the same refractive indices as the corresponding layers of the film 1640, and the layer 1747 has the same thickness as the layer 1647.
Lenslets 1744 are formed in the first structured surface 1740a, each lenslet having a vertex V as well as a focal point, a focal surface, and a focal space, which are all the same as corresponding features of the lenslets 1644, the lenslets 1744 also extending linearly along the y-axis, and having a simple curvature in the x-z plane with the same constant radius of curvature as lenslets 1644. The maximum thickness of the layer 1746 is the same as that of layer 1646, and the pitch P1 of the lenslets 1744 is the same as that of lenslets 1644.
A plurality of prisms 1741 are formed in the second structured surface 1740b. The prisms 1741 each extend linearly along an elongation axis parallel to the y-axis, and the two inclined side surfaces of each prism meet at a sharp peak or vertex. The prisms 1741 have the same prism angle θinc as that of prisms 1641; however, rather than being organized into clusters of 7 adjacent prisms, the prisms 1741 are organized into clusters 1743 of 13 adjacent prisms 1741, and rather than having a prism pitch P3 of 4 microns, the prism pitch P3 is 2 microns. The clusters 1743 are again separated by flat surfaces 1721, and there is a one-to-one correspondence of lenslets 1744 to prism clusters 1743, associated ones of which form lenslet/prism cluster pairs 1748. The film 1740 as modeled had exactly 21 complete pairs 1748. The vertex of the prism 1741 located centrally within each cluster 1743 serves as the cluster vertex Vcluster. This centrally located prism, as well as the twelve other prisms 1741 in the cluster, all have zero tilt with respect to the z-axis. The prism vertices in a given cluster 1743 are all located in the focal space of the associated lenslet 1744, where the focal space is defined in the same way as before. The prism vertices in a given cluster 1743 are coplanar. The pitch P2 of the prism clusters 1743 is the same as the pitch P2 of the prism clusters 1643, and the prism clusters 1743 and the lenslets 1744 are also aligned or registered with respect to each other.
The overall thickness or caliper D of the film 1740 was the same as the corresponding dimension of the film 1640.
The same oblique input light used in connection with the film 1640 was then injected into the second structured surface 1740b of the film 1740.
As can be seen in at least
In other cases, the rapid fluctuations may be undesirable, and a flat or flatter intensity distribution between the sharp left and right edges may be the desired. That is, the desired output may be a top hat distribution in a plot of intensity versus angle, with a high intensity that is maintained with little or no variation between the sharp left and right edges. Moreover, it may be desirable for the angular separation between the left and right edges of the light output to be substantially greater than a single spike-shaped lobe, but still limited in extent, e.g., in a range from 10 to 50 degrees, or from 20 to 40 degrees, for example. Top hat distributions such as this may be obtained with any of the disclosed optical films by adding a limited or controlled amount of light scattering. The scattering may be low enough so that the left and right edges of the light output are still sharp, but high enough so that the fluctuations between those edges mix or blend together to provide a much more uniform (flatter) intensity level. For example, the diffusion may have a FWHM angular spread of 10 degrees or less, such as provided by light shaping diffuser optical films available from Luminit, LLC, with 0.5 degree, 1 degree, 5 degree, or 10 degree FWHM diffusers. The sharpness of the left and right edges may be defined in terms of the transition angle between the 10% and 90% intensity levels, as discussed in commonly assigned U.S. patent application Ser. No. 13/850,276, “Dual-Sided Film with Compound Prisms”, filed Mar. 25, 2013. With a controlled diffuser, the 10%-to-90% transition angle for the left edge, and for the right edge, may be held to no more than 10 degrees.
A schematic view of a system in which one of the disclosed films is combined with a controlled amount of light scattering is shown in
In
The term “intensity” as used herein may refer to any suitable measure of the brightness or strength of light, including both standard (cosine-corrected) luminance and non-cosine-corrected luminance, and radiance (cosine-corrected and non-cosine-corrected).
Numerous modifications can be made to, and numerous features incorporated into, the disclosed dual-sided optical films, light guides, and related components. For example, any given structured surface of the dual-sided optical film or of the light guide may be spatially uniform, i.e., the individual elements or structures of the structured surface may form a repeating pattern that occupies the entire major surface of the component. See e.g.
In other alternatives, with a suitably designed light guide, two dual-sided optical films can be used on opposite sides of the light guide. The light guide may be configured to provide oblique light beams from each of its two opposed major surfaces, and one dual-sided film can be provided at each major surface of the light guide to convert the oblique light beam to a fan-shaped light output (including in some cases a top hat angular distribution) on each side of the light guide. For example, in
In other alternatives, the optical system may also include secondary structures to limit or reduce the degree of light spreading of the light output produced by the dual-sided optical film. For example, a conventional louvered privacy film and/or a shroud (e.g. including one or more light blocking members) may be provided at the output of the dual-sided film. These secondary structures may operate by occluding a portion of a given initial light output in the x-z plane and/or in the y-z plane to produce a modified output beam, the modified output beam being narrower than the initial output beam in the plane(s) of occlusion.
The light guide and the dual-sided optical film may both be substantially planar in overall shape, or one or both may be non-planar. Exemplary lighting system embodiments are schematically depicted in
Unless otherwise indicated, all numbers expressing quantities, measurement of properties, and so forth used in the specification and claims are to be understood as being modified by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and claims are approximations that can vary depending on the desired properties sought to be obtained by those skilled in the art utilizing the teachings of the present application. Not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, to the extent any numerical values are set forth in specific examples described herein, they are reported as precisely as reasonably possible. Any numerical value, however, may well contain errors associated with testing or measurement limitations.
Any direction referred to herein, such as “top,” “bottom,” “left,” “right,” “upper,” “lower,” “above,” below,” and other directions and orientations are used for convenience in reference to the figures and are not to be limiting of an actual device, article, or system or its use. The devices, articles, and systems described herein may be used in a variety of directions and orientations.
Various modifications and alterations of this invention will be apparent to those skilled in the art without departing from the spirit and scope of this invention, and it should be understood that this invention is not limited to the illustrative embodiments set forth herein. The reader should assume that features of one disclosed embodiment can also be applied to all other disclosed embodiments unless otherwise indicated. It should also be understood that all U.S. patents, patent application publications, and other patent and non-patent documents referred to herein are incorporated by reference, to the extent they do not contradict the foregoing disclosure.
This document discloses numerous embodiments, including but not limited to the following:
Item 1 is an optical film having opposed first and second structured surfaces, the optical film comprising:
-
- a plurality of elongated lenslets formed on the first structured surface, the lenslets being elongated along respective lenslet axes which are parallel to an elongation axis; and
- a plurality of elongated prisms formed on the second structured surface, the prisms having respective elongated prism vertices which are also parallel to the elongation axis;
- wherein the prisms are grouped into prism clusters that are separated from each other, each prism cluster having at least three of the prisms, and each prism cluster being associated with a corresponding one of the lenslets;
- wherein each lenslet defines a focal surface, and wherein for each lenslet, the prism vertices of the prisms in the prism cluster associated with the lenslet are disposed at or near the focal surface.
Item 2 is the film of item 1, wherein for each lenslet, the lenslet has an axial focal length, and a focal space encompasses the focal surface and has boundaries that are separated from the focal surface by a differential distance DD equal to 20% of the axial focal length, and wherein the prism vertices of the prisms in the prism cluster associated with the lenslet are disposed in the focal space of the lenslet.
Item 3 is the film of item 2, wherein, for each lenslet, the prism vertices of the prisms in the prism cluster associated with the lenslet are disposed in a portion of the focal space between the focal surface and the lenslet.
Item 4 is the film of item 1, wherein for each lenslet, the prism vertices of the prisms in the prism cluster associated with the lenslet lie in a plane.
Item 5 is the film of item 1, wherein for each lenslet, the focal surface has a first curved shape in a cross-sectional plane perpendicular to the elongation axis.
Item 6 is the film of item 5, wherein, for each lenslet, the prism vertices of the prisms in the prism cluster associated with the lenslet are arranged along a second curved shape in the cross-sectional plane.
Item 7 is the film of item 6, wherein the first and second curved shapes are both concave or both convex.
Item 8 is the film of item 1, wherein each prism cluster includes 5 of the prisms.
Item 9 is the film of item 8, wherein each prism cluster includes 10 of the prisms.
Item 10 is the film of item 1, wherein the prism clusters each contain a same number N of the prisms, where N is at least 3, or at least 5, or at least 10.
Item 11 is the film of item 1, wherein for each lenslet, the associated prism cluster has N of the prisms, and the lenslet cooperates with its associated prism cluster to provide, when the second structured surface is illuminated with oblique light from a first light source, a first lenslet light output defining N angularly separated light beams, and N is at least 3.
Item 12 is the film of item 11 in combination with a diffuser film disposed to receive the first lenslet light output and to convert the N angularly separated light beams to one light beam.
Item 13 is the film of item 1, wherein the optical film defines a film plane and a thickness axis is perpendicular to the film plane, and wherein at least some of the lenslets have a compound curvature in a cross-sectional plane perpendicular to the elongation axis, such lenslets also having respective lenslet axes of symmetry in the cross-sectional plane, and wherein at least some of the lenslet axes of symmetry are tilted relative to the thickness axis.
Item 14 is the film of item 1, wherein the optical film defines a film plane and a thickness axis is perpendicular to the film plane, and wherein the prisms have respective prism axes of symmetry in a cross-sectional plane perpendicular to the elongation axis, and wherein at least some of the prism axes of symmetry are tilted relative to the thickness axis.
Item 15 is the film of item 1, wherein the lenslets are spaced according to a lenslet pitch and the prism clusters are spaced according to a cluster pitch, and wherein the lenslet pitch equals the cluster pitch.
Item 16 is the film of item 1, wherein the lenslets are spaced according to a lenslet pitch and the prism clusters are spaced according to a cluster pitch, and wherein the lenslet pitch does not equal the cluster pitch.
Item 17 is the film of item 1 in combination with a diffuser film disposed proximate the first structured surface.
Item 18 is an optical system, comprising: - the optical film of item 1; and
- a light guide having a major surface adapted to emit light preferentially at oblique angles;
- wherein the optical film is disposed proximate the light guide and oriented so that light emitted from the major surface of the light guide enters the optical film through the second structured surface.
Item 19 is the optical system of item 18, further comprising a first and second light source disposed proximate respective first and second opposed ends of the light guide, the first and second light sources providing different respective first and second oblique light beams emitted from the major surface of the light guide.
Item 20 is the optical system of item 18, wherein the optical film and the light guide are non-planar.
Item 21 is the optical system of item 18, wherein the optical film and the light guide are flexible.
Item 22 is the optical system of item 18, wherein the optical film is attached to the light guide.
Claims
1. An optical film having opposed first and second structured surfaces, the optical film comprising:
- a plurality of elongated lenslets formed on the first structured surface, the lenslets being elongated along respective lenslet axes which are parallel to an elongation axis; and
- a plurality of elongated prisms formed on the second structured surface, the prisms having respective elongated prism vertices which are also parallel to the elongation axis;
- wherein the prisms are grouped into prism clusters that are separated from each other, each prism cluster having at least three of the prisms, and each prism cluster being associated with a corresponding one of the lenslets;
- wherein each lenslet defines a focal surface, and wherein for each lenslet, the prism vertices of the prisms in the prism cluster associated with the lenslet are disposed at or near the focal surface.
2. The film of claim 1, wherein for each lenslet, the lenslet has an axial focal length, and a focal space encompasses the focal surface and has boundaries that are separated from the focal surface by a differential distance DD equal to 20% of the axial focal length, and wherein the prism vertices of the prisms in the prism cluster associated with the lenslet are disposed in the focal space of the lenslet.
3. The film of claim 1, wherein for each lenslet, the focal surface has a first curved shape in a cross-sectional plane perpendicular to the elongation axis.
4. The film of claim 3, wherein, for each lenslet, the prism vertices of the prisms in the prism cluster associated with the lenslet are arranged along a second curved shape in the cross-sectional plane.
5. The film of claim 4, wherein the first and second curved shapes are both concave or both convex.
6. The film of claim 1, wherein the optical film defines a film plane and a thickness axis is perpendicular to the film plane, and wherein at least some of the lenslets have a compound curvature in a cross-sectional plane perpendicular to the elongation axis, such lenslets also having respective lenslet axes of symmetry in the cross-sectional plane, and wherein at least some of the lenslet axes of symmetry are tilted relative to the thickness axis.
7. An optical system, comprising:
- the optical film of claim 1; and
- a light guide having a major surface adapted to emit light preferentially at oblique angles;
- wherein the optical film is disposed proximate the light guide and oriented so that light emitted from the major surface of the light guide enters the optical film through the second structured surface.
8. The optical system of claim 7, further comprising a first and second light source disposed proximate respective first and second opposed ends of the light guide, the first and second light sources providing different respective first and second oblique light beams emitted from the major surface of the light guide.
9. The optical system of claim 7, wherein the optical film and the light guide are non-planar.
10. The optical system of claim 7, wherein the optical film and the light guide are flexible.
Type: Application
Filed: Sep 3, 2014
Publication Date: Jul 14, 2016
Inventor: Michael J. Sykora (New Richmond, WI)
Application Number: 14/913,120